On Fri, Jun 23, 2017 at 12:16 AM, Hal Murray <hmur...@megapathdsl.net> wrote:
> > hol...@hotmail.com said: > > The PI does have a couple of logic level serial ports on the expansion > > connector you can connect a level shifter two. One port is normally the > > Linux serial console which you can configure to be a general purpose > serial > > port (I've never used them, but others have). > > The console port used by the GPS HATs. Works fine. /dev/ttyAMA0 > > The PPS pin varies depending on which type of HAT you get. > The RaspberryPi 3 is a bit different. All the Pi models, 1 & 2 & 3, have two UARTs: a full-featured UART, and a mini-UART. On the PI 3, the header pins for the serial port are routed by default to the mini-UART, and the full-featured UART is used for Bluetooth. On the older Pi models, the full-featured UART is routed to the header, It is possible to swap them back via software, but then you lose Bluetooth functionality. The mini-UART has issues with its baud-rate generator: it is derived from the system clock, not an independent clock generator like the full-featured UART, so it doesn't work when dynamic system clocking for power management is enabled, so you either have to run at max or minimum speed only. FWIW, I'm running a custom Fedora 25 on all my Pi3, as the default doesn't support all Pi3 devices (and I don't want the U-Boot boot-loader either). I'm using cheap $0.99 USD CH340 based USB-to-Serial converters from E-Bay (I bought 10), as well as my bench equipment which are mostly FTDI (hacked some to use standard VendorId and DeviceId) or PL. Beware that USB-to-Serial converters are pretty horrible for precise timing applications, like PPS on the CD pin. It can be done on a GPIO pin instead, but requires some hacking and re-compiling. _______________________________________________ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.